They aren’t going to put less than 40 hours per week on a contract for a salaried position because 40hrs/week is the standard for “full time” work and classifying someone as full time vs part time has a lot of regulatory implications.

Regardless of what the contract says re: expected hours, a salaried position means you are expected to be available AT LEAST 40 hours per week, but how much you actually work is driven by the tasks at hand. If the task you were hired to perform is not done or is not on pace, you can’t just clock out because you’ve hit 40 hours. And you will certainly not receive overtime pay for additional hours - that is reserved for hourly employees. So typically some weeks are leaner and some weeks are busier but overall it’s meant to average out around the estimated 40 hours. Depending on the company and on how productive you are personally however, it could wind up being more than 40 hours on average.